The present invention relates to computer systems including a plurality of storage systems. More particularly, the present invention relates to a computer system that has a remote copy function of copying data stored in a storage system into another storage system and that is capable of controlling power supply to a storage device to suppress the power consumption and to a method of reproducing data for the computer system.
Two technologies including remote copy and power supply control for a storage device will be described as related arts of the present invention.
First, the remote copy will be described.
The remote copy is a technology of copying data (original data) written in a storage system by a superior device, such as a computer, into another storage system. Such a technology is required for disaster recovery (recovery of an information system destroyed by large scale natural disaster) and data backup.
One remote copy technology disclosed in Japanese Unexamined Patent Application Publication No. 2005-18506 (Patent Document 1) will now be described. It is assumed that a computer system includes the following three components:    (1) a computer,    (2) a first storage system, which is connected to the computer and in which the computer records data that is modified by the computer (the data is referred to as original data), and    (3) a second storage system that is connected to the first storage system and that stores a copy of the original data.
In the above computer system, the computer requests the first storage system to modify the original data. The first storage system generates information (a journal) concerning update of the original data and temporarily stores the generated journal in a storage area of the first storage system. The second storage system requests the first storage system to transmit the journal and updates the copy with the received journal.
The second storage system acquires the journal from the storage area asynchronously with access from the computer (journal read) in order to prevent performance deterioration due to the remote copy in access to the original data by the computer.
A function of copying data of the storage system by the remote copy technology is hereinafter simply referred to as the remote copy. A storage system having original data to be copied recorded therein is referred to as a main storage system, and a storage system in which the copied data is recorded is referred to as a sub storage system.
The remote copy in which data written by a superior device is simultaneously reflected in the original data and a copy of the original data is referred to as synchronous remote copy. The remote copy in which writing of data in the copy is not performed simultaneously with writing of the data in the original data is referred to as asynchronous remote copy.
Next, the power supply control for a storage device will be described.
The power supply control for a storage device is a technology of turning off the storage device in a storage system in accordance with the frequency of access to the storage device or the presence of the access to reduce the power consumed by the storage system and to extend a time period (hereinafter referred to as a mean life) before a failure of the storage device occurs.
The storage device is a device capable of recoding and reading out electronic data. A hard disk drive is exemplified as the storage device according to embodiments of the present invention. The power supply control includes strategies of reducing access delays caused by the storage device that is turned off, and of maintaining the state in which the storage device is turned off as much as possible.
One power supply control technology for a storage device is disclosed in Japanese Unexamined Patent Application Publication No. 2005-157710 (Patent Document 2).
In this power supply control technology, a storage system is provided with an interface through which an external computer that is connected to the storage system and that records data in the storage system can request turning on/off of a specified storage device (a logical volume (described below) is actually specified as the storage device). Specifically, the computer requests the storage system to turn off a storage device that is found not to be accessed for some time, among storage devices in the storage system, through the interface.
Another power supply control technology is disclosed in United States Patent No. 2004/0054939 (Patent Document 3).
A storage system basically turns off storage devices as long as the storage devices are not accessed. In order to increase the number of storage devices that is turned off, a data recording technology resulting from modification of Redundant Arrays of Inexpensive Disks (RAID) Level 4 is used. In order to reduce the access delays, a parity disk (a storage device in which error correction information is recorded) and a metadata disk (a storage device in which information concerning the structure inside the storage system and data cache are recorded), which disks adopt the above data recording technology, are always turned on.
When the remote copy is used to copy data recorded in the main storage system into the sub storage system, the storage device in which the copied data is recorded may be turned off while update of the storage device is not required. Accordingly, application of the power supply control technology for the storage device to the sub storage system will be reviewed.
In the technology disclosed in Patent Document 2, the computer instructs turning on/off of the storage device. Hence, the technology disclosed in Patent Document 2 is not appropriate for the asynchronous remote copy disclosed in Patent Document 1, that is, the remote copy in which copying of data is performed between the storage systems asynchronously with the access from the computer.
The technology disclosed in Patent Document 3 requires the storage devices that are always turned on. Such storage devices increase the power consumption in the storage system and shorten the mean life of the storage devices in the storage system.